chore: update Anchor version

Author: beeman

.github/workflows/ci.yml

@@ -30,7 +30,7 @@ jobs:
           cache: 'pnpm'
       - uses: metadaoproject/setup-anchor@v2
         with:
-          anchor-version: '0.30.1'
+          anchor-version: '0.31.1'
           solana-cli-version: '1.18.9'
           node-version: '20.10.0'
       - run: pnpm install --no-frozen-lockfile